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Advances in Materials Science and Engineering
Volume 2016 (2016), Article ID 1745839, 7 pages
Research Article

Microstructural Changes during High Temperature Service of a Cobalt-Based Superalloy First Stage Nozzle

1Instituto de Investigaciones Eléctricas, Reforma 113, 62490 Cuernavaca, MOR, Mexico
2CIICAp, Universidad Autónoma del Estado de Morelos, Avenida Universidad 1001, 62209 Cuernavaca, MOR, Mexico
3Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Avenida Universidad s/n, 62210 Cuernavaca, MOR, Mexico
4Corrosion y Protección (CyP), Buffon 46, 11590 Ciudad de México, DF, Mexico

Received 30 October 2015; Revised 7 March 2016; Accepted 8 March 2016

Academic Editor: Amit Bandyopadhyay

Copyright © 2016 A. Luna Ramírez et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Superalloys are a group of alloys based on nickel, iron, or cobalt, which are used to operate at high temperatures ( > 540°C) and in situations involving very high stresses like in gas turbines, particularly in the manufacture of blades, nozzles, combustors, and discs. Besides keeping its high resistance to temperatures which may approach 85% of their melting temperature, these materials have excellent corrosion resistance and oxidation. However, after long service, these components undergo mechanical and microstructural degradation; the latter is considered a major cause for replacement of the main components of gas turbines. After certain operating time, these components are very expensive to replace, so the microstructural analysis is an important tool to determine the mode of microstructure degradation, residual lifetime estimation, and operating temperature and most important to determine the method of rehabilitation for extending its life. Microstructural analysis can avoid catastrophic failures and optimize the operating mode of the turbine. A case study is presented in this paper.